1. Field of the Invention
The present invention relates to a pressure sensitive sensor and manufacturing method thereof.
2. Description of Related Art
In a power sliding door apparatus (also known as an electric sliding door apparatus), a door panel is driven by a drive force outputted from an electric motor to open or close an entrance/exit opening (also known as a sliding door opening) of a vehicle. It has been proposed to place a pressure sensitive sensor (also known as a pinch sensor) at the door panel to sense presence of an foreign object (e.g., a human body) between an inner peripheral part of the entrance/exit opening of the vehicle and the door panel to limit pinching of the foreign object between the inner peripheral part of the entrance/exit opening and the door panel.
For instance, Japanese Unexamined Patent Publication No. H11-283459A (corresponding to U.S. Pat. No. 6,339,305B1) and Japanese Unexamined Patent Publication No. 2004-342456A teach such a pressure sensitive sensor that includes an elongated sensor cable, which is placed along a front end part of the door panel. The elongated sensor cable includes a plurality of electrode wires, which are received in a resiliently deformable elongated hollow dielectric body and are connected in series through a resistor. In this type of pressure sensitive sensor, two electrode wires are pulled out from a proximal end part of the hollow dielectric body and are electrically connected to one end parts of power supply lead lines, respectively, through clamping pieces (caulking pieces) at a terminal coupler. Here, each of the clamping pieces is radially inwardly bent to clamp a corresponding one of the electrode wires and a corresponding one of the one end parts of the power supply lead lines. Furthermore, at each of the clamping pieces, the electrode wire and the one end part of the power supply lead line are securely joined to the clamping piece by welding. The other end parts of the lead lines, which are opposite from the terminal coupler, are connected to an electrical power source, so that electric current is supplied from the electric power source to the electrode wires through the lead lines. In general, the lead lines are connected to the electric power source through a power supply connector, which is provided to the other end parts of the lead lines opposite from the terminal coupler.
In this type of pressure sensitive sensor, when the foreign object does not contact the sensor cable, the electrode wires, which are received in the hollow dielectric body, do not contact with each other. Thereby, the electric current, which is supplied through the lead lines (power supply lines), flows from one of the electrode wires, which has a high electric potential, to the other one of the electrode wires, which has a low electric potential, through the resistor. In contrast, when the foreign object contacts the sensor cable to apply an urging force against the sensor cable, the electrode wires, which are received in the hollow dielectric body, contact with each other to cause short circuiting therebetween. Thereby, the electric current, which is supplied through the lead lines (power supply lines), flows from the one of the electrode wires, which has the high electric potential, to the other one of the electrode wires, which has the low electric potential, without passing through the resistor. In this way, a current value of the electric current, which is supplied to the electric wires at a predetermined constant voltage, is changed. Thereby, the urging force, which is applied from the foreign object to the sensor cable, is sensed based on this change in the current value. That is, the foreign object, which contacts the sensor cable, is sensed based on the change in the electric current.
However, in the case of the pressure sensor, in which the power supply lead lines are connected to the sensor cable in the above described manner, the lead lines and the terminal coupler, which includes the multiple components, are connected to the end part of the sensor cable. Therefore, the number of the components is disadvantageously increased. Furthermore, at the time of electrically connecting the electrodes of the electrode wires and the lead lines, each of the electrodes and the corresponding clamping piece are joined, together by welding, and each of the lead lines and the corresponding clamping piece are joined together by welding. Therefore, the work required for connecting the electrodes and the lead lines becomes disadvantageously tedious. This may possibly result in a reduction in the productivity. Thereby, the manufacturing costs may be disadvantageously increased.